This invention relates to a light-transmitting screen and more particularly to a viewing screen which is capable of directing and focusing light images falling thereon.
A directional reflector device is known which comprises a multitude of minute glass balls applied to one surface of the reflector layer. When this device is used as a screen on which a picture is projected for viewing, the rays of light reflected by the screen converge in a position near the projector. Since the reflection by the screen is directional, it is possible to discriminate between the various picture images formed on the screen by a plurality of projectors projecting a plurality of pictures in superposed relationship. Generally, however, the viewer must be positioned near the projectors, so that the projectors may interfere with his field of view.
A screen or light transmitting system wherein a convex lens or Fresnel lens generally referred to as a field lens is utilized, has hitherto been used as a device for viewing picture images without being disturbed by the presence of projectors. However, this screen has a disadvantage in that it is impossible to obtain a large size screen. An additional disadvantage is that the screen itself has a central optical axis so that it is difficult to obtain a good view in any position other than that on the optical axis. Besides, when a plurality of projectors are used for projecting a plurality of pictures, the point of convergence of light rays relative to the projector is symmetrically displaced both vertically and horizontally with respect to the optical axis. Furthermore, a large number of screens must be arranged in the same plane to provide a screen unit of large area. When a picture is projected onto such a screen unit, the rays of light will converge in a number of positions so that it becomes impossible to view the entire image at once in one position.
The aforementioned disadvantages of screens of the light transmitting type comprising field lenses or Fresnel lenses are directional reflector devices utilizing spherical bodies of glass can be obviated if a multitude of screen elements each of which is a small lens system of predetermined size are arranged in a plane to form a large screen of the type which has no optical axis of its own so that rays of light projected from one side on the screen from any position as desired may be transmitted by the screen and made to converge at a number of selected positions or on one spot on the other side of the screen which is disposed in a position corresponding to the position of the projection light source with respect to the screen.